Phyllosilicate minerals such as kaolinite, talc, chlorite, pyrophyllites and montmorillonite are minerals which contain basic silicates and are used in a variety of applications such as paper manufacturing, talcum powder, tailor's "chalk", cosmetics, and lubricants.
With regards to talc, a slurry of talc is commonly used in paper manufacturing to control, inter alia, pitch. To manufacture these slurries, talc is added to water until a suspension having a desired solids content is produced. This process is conventionally referred to as a "makedown" process. Currently available makedown processes yields a talc slurry having about 25-45% solids with a reasonable viscosity.
A large quantity of talc is often used in the paper and other industries; therefore, reduction of the transportation cost of such material to the customer is the subject of considerable effort. High solids slurries of talc are desirable because it increases the transportation cost effectiveness. However, settling occurs when talc slurries are permitted to stand without agitation. In addition, high solids content talc slurries produced by the current methods are too viscous and form a thick mass or gel after several days, which requires the customer to employ extensive mechanical devices to redisperse the slurries or use various chemicals to render the slurries usable. Often, the slurries are returned to the manufacturer as unacceptable.
U.S. Pat. No. 5,424,259, issued to Yordan et al., discloses a method of making a kaolin clay slurry having at least 50% by weight of kaolin clay by mixing water and a lithium based dispersant and then mixing structured kaolin clay particles with the aqueous composition to form the desired high solids slurry.
U.S. Pat. No. 4,118,246, issued to Horzepa et al., discloses a process for producing kaolin clay slurry having 60% to 70% by weight of kaolin clay using a dispersant and a micromixer. This process requires a use of the special micromixer apparatus.
U.S. Pat. No. 4,144,083, issued to Abercrombie, Jr., provides a method for maintaining the low shear viscosity of a kaolin clay slurry having 60% to 72% by weight of kaolin clay using 0.5 to 3.0 pounds of citric acid or sodium citrate per ton of kaolin clay.
U.S. Pat. No. 4,186,027, issued to Bell et al., discloses a process for making kaolin slurry at pH from 7.5 to 10.5, having a solids content in the range of from 60% to 75% by weight using a dispersing agent and a water-soluble organic polymer. The slurry is subjected to a particle size separation to reduce the percentage of the particles larger than 10 .mu.m in the slurry to not more than 3% by weight.
U.S. Pat. No. 4,309,222, issued to Hoyt, IV, provides a method for making a kaolin slurry of reduced low shear viscosity in water at a pH of 6 to 8 having a solids content from about 60% to 72% using citrate and polyacrylate.
U.S. Pat. No. 4,650,521, issued to Koppelman et al., provides a process for making a kaolin slurry having a solids content of at least about 65% using a carbonate, a water-soluble organic polyacrylate and a water-soluble anionic phosphate. The slurry is then subjected to a "degritting" process to reduce the percentage of the particles larger than 45 .mu.m in the slurry to not more than 0.2% by weight.
U.S. Pat. No. 4,374,203, issued to Thompson et al., provides a method for making a clay slurry having at least 50% by weight of the clay using anionic and cationic polymers.
However, for various reasons such as a need for the use of organic polymers, special mixers and/or a need for particle size separation, the prior art fails to provide an acceptable process for producing low cost high solids phyllosilicate mineral slurries having desired rheological properties. Therefore, there is a need for an inexpensive method of preparing a phyllosilicate slurry having a high solids content and low viscosity.